Glow switch for starting discharge devices



MayZZ, 1945. DE T O 2,376,669

GLOW SWITCH FOR STAR TING DISCHARGE DEVICES Filed Feb. 28, 1944 Inventor: Nicholas DeToro,

Patented May 22,- 1945' UNITED STATES PATENT OFFICE lilcholaabe'l'ormliridmconnqm General Beetrlc company, a corporation of New York Application February 28,1944,

(Claims. (01.200-1 35) My invention relates to glow switches for starting discharge devices, such for example as fluorescent lamps, and it has for its object the provision of an improved construction of switches for that purpose enabling one to obtain a faster starting 01 the devices and a minimum of polarization of the interelectrode gaseous conduction;

My invention will be better understood from the following description taken in connection with the accompanying drawingand its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a side view a partly in section of a switch embodying my invention and Fig. 2 is a circuit diagram including the switch and apparatus connected therewith, In the drawing, l is an envelope which may be constructed of glass containing an ionizablemedium such for example as neon at a low pressure. Secured in the press 2 oi'the envelope are the two leads 8 and l, and the support 5.. Welded or otherwise suitably secured at one end to the support 5 is the fiat bimetallic thermal strip t, the opposite end being provided with the contact I which normally engages the cooperating fixed contact 8 on the lead]. The strip 6 is'constructed with the metal having the greater coef through the control switch II and the ballast particularly the adjacent parts thereof, accordingly begin to heat up, the strip l more rapidly than the strip 6 because of its smaller mass. Because of the tendency of the strip 8 to deflect, the contact 'I thereon engages the contact 0 with less pressure; strip 0, however, being more sensitive deflects so that its contact II soon touches the contact H on the other strip therebyshort circuiting the glow discharge but even though that source or. heat is extinguished the strip 8 conficient of thermal expansion on that side thereof wherebywhen the temperature of that part of the strip adjacent to the other strip I is raised the cooperating contacts I and 8 tend to disengage. Welded or otherwise secured to the other lead I is a second fiat bimetallic thermal strip 9 which is provided with the contact l8 facing the thermal strip 3. The strip is constructed so of electron emission.

tinues to deflect due to heat inertia and to the resistance heating of the strip by the flow there through oi the lamp electrode preheating current until the contacts 1 and t are caused to separate. During the interval of ent of the contacts l0 and H and before thecontacts I and 8 separate the filaments II are heated to the point The opening of the circuit at the contacts I and 8 causesthe lamp -tostartaf whichbyreasonotthecoolingot thetwostrips,thatofthestrlplbeingmore rapidthanthatoithestrip l,thecontacts II with the metal having the greater coeflicient of 35 and II first separate th n h M 1 and thermal expansion on that side thereof whereby when the temperature of thatpart of the strip adjacent to the other strip 0 is raised it willbe deflected toward the other strip and its contact 10 will engage the contact I I on the other strip. The two strips 8 and I preferably are similar as to form and as to the metals employed but diiler from each other in that they have different thicknesses, the strip I being the thinner oi the two whereby it has less mass and is the more sensitive to temperature changes. The two strips are coated with a high electron emission film except that no coating is applied to the contact I or to the end portion of the strip 8 adjacent to that contact. Also, no film is applied to the lead 3.

In the circuit diagram shown by Fig. 2, J2 rep-.

lamp, having the electrodes II connected to be re-engage. Incontiasttoaformolaglowswitch attincommonusetorstartingfiuorescent lampsthecurrentfiowduiingtheglowdischarge tivelygreat,forbothelectrodes,tliatlsboththermalstrlpslandlarecoatedwiththeclectron emissionfilmsothatthedischargeoccursduring both halt'cycles, the electrodes being non-recti- 5 lying, and both M13 havesubstantlally the at large surface area. Greater speed or operation naturally results n'omtheproductlmotthc g'mterheatblthellwdischm liwmbe Wruptedatatimewhenthereisnoimiisatlonin notedthatthelampelectrodecircuitisintertheenvelcpeandtheinterruptionoocnrsinaresion where the cooperating crntact members presentsmallareastoeachothm'andhvesub facesotelectronicrates. As

s pp ied from a source of alternating current I4 a result-and in further contrast to present day starters my switch is effective to start the lamp equally well on either half cycle. The thermal strips 6 and 9 are constructed and spaced apart and the gas employed is such that ionization occurs at a suitable voltage which, in the case of a 40 watt lamp on a 118 volt supply circuit, may be 170 volts. After the contacts In and II have closed extinguishing the glow the inductive voltage produced across the contacts I and 8 by their subsequent opening and. hence that applied to the lamp to start it may be as high as 1000 volts for since the parts adjacent to those contacts are not coated a glow discharge does not readily form in the envelope the effect of which would be to shunt the lamp. The diameter of the lead 3 and hence its exposed surface may, moreover, be very small, materially smaller than the wire electrodes of present day starters which require a certain minimum surface.

After the lamp has started, the voltage across it is insufficient to ionize the space between the two thermal strips; if it fails to start the starting cycle is automatically repeated as soon as the contacts 1 and 8 re-engage. contacts In and II being already separated.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A glow discharge starting switch comprising an envelope containing an ionizable medium. a plurality of thermal members mounted in said envelope and having adjacent portions arranged to be deformed in the same direction by heat of a glow discharge therebetween, one of said members being more sensitive than the other, a fixed contact in said envelope, 9. cooperating contact carried by the other thermal member of less sensitivity and a contact carried by said thermal member of more sensitivity and arranged when that member is deformed by heat of the discharge to engage the other thermal member and to cause' said cooperating contact to disengage said fixed contact.

2. A glow discharge starting switch comprising an envelope containing an ionizable medium, a

first thermal strip mounted therein having a contact at one end, a cooperating fixed contact, a second thermal strip more sensitive than said first strip and mounted adjacent thereto, said strips being constructed to be deformed in the same direction in response to heat from a discharge between them, and said second strip having a contact operable when the strip is deformed to engage the first strip and to move its contact away from said fixed contact.

3. A glow discharge starting switch comprising an envelope containing an ionizable medium, a plurality of thermal membershaving coatings of electron emitting material, each secured at one end in said envelope, said members being constructed to move their opposite ends in the same direction in response to heat produced by a glow discharge between them and the one member being more sensitive than the other and a fixed contact normally engaged by the less sensitive member, said .member of greater sensitivity being arranged to be deflected in engagement with the other member in response to heat of the discharge whereby the discharge is extinguished and by its continued deflection to separate said less sensitive member from said fixed contact.

4. A glow discharge starting switch comprising an envelope containing an ionizable medium, a first thermal strip mounted at one end therein, a slender fixed contact member arranged nor mally to be engaged by the opposite end portion of said strip, a second thermal strip more sensitive than said first strip mounted at one end in said envelope and arranged when deflected by the heat of a discharge between said strips to engage said first strip and move said opposite end portion out of engagement with said fixed contact member, and a coating of electron emitting material on each of said strips, that portion of said first strip adjacent said fixed contact member being devoid of said coating whereby a higher voltage is required to produce a discharge between it and the fixed contact.

' NICHOLAS DE TORO. 

